1. Field of the Invention
The present invention relates to a method for producing an alumina template of nanorods, the alumina template, and the nanorods thereof, in particular to the alumina template that contains an inert metal and an active metal as a conductive substrate, the method for producing the alumina template, and the method of producing nanorods by the alumina template.
2. Description of the Related Art
To produce nanorods from an alumina template is a known technology. In the process of producing the alumina template, an anodic oxidation technology is applied, and such technology relates to an electrochemical etch reaction. Aluminum is immersed in an acid solution under an electrical field, and the aluminum turns into Anodic Aluminum oxide, AAO. The structure of AOO is similar to a honeycomb with hexagonal single cells and straight holes perpendicular to the template, and a non-conductive barrier layer is formed at the bottom of the hole by oxidation. The barrier layer must be removed before the AAO can be grown into nanorods. However in the process of removing the barrier layer, the following issues arise: AAO is peeled off and the substrate material is oxidized. If an inert metal such as nickel is used as a conductive substrate material during over etch and enlarging hole processes, the inert metal is not easy to be oxidized, the etch occurred on both sides of AAO causes an AAO strip by undercutting. If an active metal such as titanium is used as the conductive substrate, the over etch will not cause the AAO strip, but the active metal will be oxidized and non-conductive oxides will be generated easily, thus causing difficulties to subsequent electroplating process. A better way to solve the above issues is to step down the voltage at the end of anodic oxidation to thin the barrier layer, such that the barrier layer can be removed more easily after the etching. However, the bottom of the holes becomes thinner and has discrepancy which may weaken the support of the subsequent electroplating of nanorods. In addition, the timing of stepping down the voltage is also difficult to control. Obviously, this is not a good method.